Sliding contact surface-forming material, slide bearing containing same, and method of using same in a moist environment

ABSTRACT

A sliding contact surface-forming material, and method of making the material are disclosed, the material having minimal swelling and excellent friction-proof and wear-proof characteristics when used in moist environments such as in water, and improved in the friction-proof and wear-proof characteristics under dry friction conditions such as in the open air, particularly under oscillation conditions for testing journal. The material includes a reinforcing base impregnated with a resol-type phenolic resin having polytetrafluoroethylene resin dispersed therein. The reinforcing base is composed of a woven fabric formed by using, as each of the warp and the weft, a ply yarn which is formed by paralleling at least two strands of a single twist yarn spun from fluorine-containing resin fiber and a single twist yarn spun from polyester fiber, and by twisting them in the direction opposite to the direction in which the single twist yarns were spun.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of U.S. patentapplication Ser. No. 13/496,915, filed on Mar. 19, 2012, which is a U.S.National Phase of PCT International Application PCT/JP2010/004562 filedon Jul. 14, 2010, which, in turn, claimed priority based on Japanesepatent application No. 2009-228146 filed on Sep. 30, 2009. The subjectmatter of each of these priority documents, including specification,claims, and drawings, is incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to a sliding contact surface-formingmaterial used for sliding contact components such as slide bearing, anda multi-layered sliding contact component having the sliding contactsurface-forming material for the sliding contact surface thereof.

BACKGROUND ART

There have been well-known sliding contact component having flat orcircular cylindrical geometry, configured by stacking resin workmaterials each composed of cotton fabric, as a reinforcing base,impregnated with a thermosetting synthetic resin such as phenolic resinand epoxy resin, or with a resin composition composed of thethermosetting resin added with polytetrafluoroethylene resin (PatentDocument 1). The sliding contact component are adopted in a wide varietyof fields, including wear ring fitted to the outer circumferentialsurface of piston of hydraulic cylinder, underwater slide bearing and soforth, by virtue of its excellence in the wear resistance, loadresistance and rigidity. In particular, excellent performances of thephenolic resin under water lubrication are largely ascribable to thesurface characteristics thereof, and are also possibly contributed byadsorption of water to the cotton fabric used as the base, and goodaffinity of OH group of the phenolic resin with water.

The circular cylindrical multi-layered sliding contact componentmanufactured using the fiber-reinforced resin composition composed ofthe cotton fabric and the phenolic resin has, however, been facingdifficulty in keeping a constant clearance (gap of sliding contact) withrespect to the opposing shaft, when used in a humid atmosphere orunderwater, due to swelling and dimensional changes as a consequence.Such swelling of the circular cylindrical multi-layered sliding contactcomponent is mainly ascribable to high water absorptivity of the cottonfabric used as the reinforcing base. Accordingly, low-water-absorptivesynthetic fiber fabrics, composed of polyester fiber, polyacrylonitrilefiber and so forth, have attracted public attention as reinforcing basesother than the cotton fabric, intended for underwater applications. Thesynthetic fiber fabrics are advantageous also in that they arerelatively inexpensive, and express reinforcing effects on resins.

The synthetic resins having these advantages, however, suffer from theirpoor adhesiveness to resins, when intended to achieve a satisfactorylevel of reinforcing effect with respect to the resins.

Patent Document 2 discloses a fiber-reinforced resin compositionconfigured by using, as a reinforcing material, a woven fabric made ofpolyamide fiber, polyester fiber, polyacrylonitrile fiber or carbonfiber, and impregnated with a thermosetting synthetic resin such asphenolic resin added with fluorine-containing polymer, melamine resin,epoxy resin or alkyd resin, and a slide bearing using the same. In orderto improve the adhesiveness between these synthetic fibers and thesynthetic resins, the synthetic resins are added with co-condensationproducts of polyamide and polyvinyl alcohol derivatives, as adhesionenhancers.

Patent Document 3 discloses a reinforced plastic plate configured bystacking sheets of polyester fiber woven fabric, used as reinforcingbases, after being impregnated with an unsaturated polyester resin. Itis, however, difficult to adhere the intact polyester fiber to theunsaturated polyester resin, due to a poor content of functional groupsin the polyester fiber. The Patent Document 3 therefore describes that,in order to improve the adhesiveness, or affinity, of the fiber with theresin, the polyester fiber is annealed with a bisphenol-based epoxyresin adhesive in an organic solvent, at a temperature of 150° C. orbelow for 5 to 120 minutes.

Non-Patent Document 1 discloses a technique of a surface treatment forpolyester fiber described below, aiming at improving interfacialadhesiveness between a polyester fiber woven fabric as a base and aresin as a matrix in a composite material.

(1) Chemical treatment for improving wettability with RFL (resolcinolfolmaldehyde latex), for imparting reactivity, and for improvingadhesiveness, by increasing the number of carboxyl groups, hydroxygroups, and amide groups, making use of property of polyester fibersusceptible to hydrolysis, amine-assisted decomposition,alcohol-assisted decomposition, and so forth.

(2) Physical treatment using electron beam, ultraviolet radiation, orlow-temperature plasma.

(3) Surface treatment using isocyanate compounds.

(4) Surface treatment using ethylene urea, ethylene urethane, phenylurethane or the like.

(5) Surface treatment using alkali.

Problems in the above-described techniques of surface treatment forsynthetic fibers disclosed in Patent Document 2, Patent Document 3 andNon-Patent Document 1 are enumerated below:

(1) poor workability and very strong toxicity in some cases;

(2) treatment liquid is readily affected by temperature and humidity,and less stable;

(3) high cost due to need of large volume of treatment liquid; and

(4) the synthetic fibers per se are degraded in some cases.

It is therefore understood that no techniques, capable of obtainingsufficient levels of improvement in the adhesiveness and safety, havebeen established as the methods of surface treatment of syntheticfibers.

PRIOR ART DOCUMENT Patent Document

Patent Document 1: Japanese Examined Patent Publication No. S39-14852

Patent Document 2: Japanese Laid-Open Patent Publication No. H04-225037Patent Document 3: Japanese Examined Patent Publication No. S43-27504

Non-Patent Document

Non-Patent Document 1: “Fukugo Zairyo to Kaimen (Composite Materials andInterface”, edited by the Editorial Committee of Material Technology ofJapan Research Institute, p. 161-166, published on May 10, 1986, by SogoGijyutu Shuppan

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

Considering the above-described situation, the present applicantpreviously proposed a fiber-reinforced resin composition capable ofdisusing surface treatment of polyester fiber used as a reinforcingbase, and of obtaining a sufficient level of adhesiveness with respectto a phenolic resin, and a multi-layered sliding contact component, suchas slide bearing, manufactured by using the fiber-reinforced resincomposition (Japanese Laid-Open Patent Publication No. 2009-91446). Theinvention was to provide a multi-layered sliding contact componentadoptable to a wide variety of applications under dry and frictionalconditions, grease-lubricating conditions, and water-lubricatingconditions, since a specific resol-type phenolic resin mixed with apredetermined amount of polytetrafluoroethylene resin is excellent inthe affinity with polyester fiber woven fabric, so that thefiber-reinforced resin composition provided herein may be excellent inadhesiveness with respect to the polyester fiber woven fabric, excellentin friction-proof and wear-proof characteristics, high in rigidity,large in mechanical strength, and extremely small in the amount ofswelling even if used in a moist atmosphere such as in oil or water.

While the sliding contact component proposed in the above caused only anextremely small degree of swelling even if used under moist atmospherestypically in oil or water, and was excellent in friction-proof,wear-proof characteristics under such conditions, there has been a roomfor improvement in the friction-proof, wear-proof characteristics underdry frictional conditions such as in the air, particularly underoscillating conditions for testing journals. There has, therefore, beena need for improvement in the friction-proof, wear-proof characteristicsunder such conditions.

The present invention was conceived after considering theabove-described problems, an object of which is to provide a slidingcontact surface-forming material improved in the friction-proof,wear-proof characteristics under dry frictional conditions such as inthe air, particularly under oscillating conditions for testing journals,while keeping the advantages of the previously-proposed sliding contactcomponent unchanged, that is, while keeping the low swelling,friction-proof, and wear-proof characteristics under moist atmospheretypically under water unchanged, and to provide a multi-layered slidingcontact component having the sliding contact surface-forming material soas to configure the sliding-contact surface thereof.

Means for Solving the Problems

According to the present invention, there is provided a sliding contactsurface-forming material which includes a reinforcing base impregnatedwith a resol-type phenolic resin having a polytetrafluoroethylene resinpowder dispersed therein. The reinforcing base is composed of a wovenfabric formed by using, respectively as the warp and the weft, a plyyarn which is formed by paralleling at least two strands of a singletwist yarn spun from fluorine-containing resin fiber and a single twistyarn spun from polyester fiber, and by twisting them in the directionopposite to the direction in which the single twist yarns were spun.

The fluorine-containing resin fiber adoptable herein may include one ormore of polytetrafluoroethylene (referred to as “PTFE”, hereinafter)fiber, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer(referred to as “PFA”, hereinafter) fiber,tetrafluoroethylene-hexafluoropropylene copolymer (referred to as “FEP”,hereinafter) fiber and ethylene-tetrafluoroethylene copolymer (referredto as “ETFE”, hereinafter) fiber. For the case where a particularly heatresistance is necessary in applications of sliding contact component,PTFE fiber is preferably selected.

The single twist yarn spun from fluorine-containing resin fiber, usedfor configuring the reinforcing base, is preferably a yarn of at least400 denier, and the single twist yarn spun from polyester fiber, usedfor configuring the reinforcing base, is preferably a yarn having atleast No. 30 cotton count.

The single twist yarns spun from fluorine-containing resin fiber andfrom polyester fiber are preferably lower-twisted (Z-twisted) yarns, andeach of the single twist yarn spun from fluorine-containing resin fiberand the single twist yarn spun from polyester fiber preferably has atwist count of 260 to 300 T/m.

The ply yarn, which is formed by paralleling at least two strands of asingle twist yarn spun from fluorine-containing resin fiber and a singletwist yarn spun from polyester fiber, and by twisting them in thedirection (S-direction) opposite to the direction in which the singletwist yarns were spun, preferably has a twist count of 255 to 295 T/m.

The woven fabric, as the reinforcing base, formed by weaving the plyyarn is preferably a flat-woven fabric preferably having a density of 36to 44 ends/inch for the warp (vertical yarn), and 36 to 44 picks/inchfor the weft (horizontal yarn).

The sliding contact surface-forming material of the present inventionpreferably contains 35 to 50% by weight of the resol-type phenolicresin, 10 to 30% by weight of the PTFE powder, and 35 to 50% by weightof the reinforcing base (where, the contents of the three componentstotals 100% by weight).

The resol-type phenolic resin in the present invention is preferablysynthesized by allowing a phenolic compound which contains 50 to 100 mol% of bisphenol A to react with a formaldehyde compound, while beingcatalyzed by an amine compound, has a number-average molecular weightMn, measured by gel permeation chromatography, of 500 to 1000, and has adistribution index Mw/Mn, given as a ratio of weight-average molecularweight Mw and number-average molecular weight Mn, of 2.5 to 15.

The PTFE powder contained in the resol-type phenolic resin while beingdispersed therein is preferably either of a high-molecular-weightpolytetrafluoroethylene resin having a molecular weight of severalmillions to several tens of millions, or a low-molecular-weightpolytetrafluoroethylene resin having a molecular weight of severalthousands to several hundreds of thousands.

A multi-layered sliding contact component of the present invention hasthe overall shape of a flat plate and has the above-described slidingcontact surface-forming material so as to configure typically at leastthe sliding-contact surface of a square metal backing made of afiber-reinforced synthetic resin; or has the overall shape of a circularcylinder and has the above-described sliding contact surface-formingmaterial so as to configure typically at least the sliding-contactsurface of a circular cylindrical metal backing made of afiber-reinforced synthetic resin.

EFFECT OF THE INVENTION

Since the reinforcing base, which is composed of a woven fabric formedby using, respectively as the warp and the weft, a ply yarn formed byparalleling at least two strands of a single twist yarn spun fromfluorine-containing resin fiber and a single twist yarn spun frompolyester fiber, and by twisting them in the direction opposite to thedirection in which the single twist yarns were spun, allows thefluorine-containing resin fiber and the polyester fiber to expose on atleast one surface thereof which serves as the sliding contact surface,while keeping almost equal areas of exposure, so that the presentinvention successfully provides a sliding contact surface-formingmaterial, improved in the friction-proof and wear-proof characteristics,contributed also by low friction properties of the PTFE powderimpregnated into the reinforcing base.

Since the woven fabric as the reinforcing base, woven using the ply yarnas the warp and weft, may be made thicker than a flat-woven fabrictypically woven by using single twist yarn, so that the multi-layeredsliding contact component, integrally having the sliding contactsurface-forming material impregnated with a specific resol-type phenolicresin containing PTFE powder, may be subjected to machining, and therebyimproving dimensional accuracy of the multi-layered sliding contactcomponent.

The resol-type phenolic resin preferably used in the present inventionis synthesized by allowing a phenolic compound which contains 50 to 100mol % of bisphenol A to react with a formaldehyde compound, while beingcatalyzed by an amine compound, has a number-average molecular weightMn, measured by gel permeation chromatography (GPC), of 500 to 1000, andhas a distribution index Mw/Mn, given as a ratio of weight-averagemolecular weight Mw and number-average molecular weight Mn, of 2.5 to15. The phenolic resin exhibits a good affinity with the hydrophobicpolyester fiber, so that it may thoroughly be impregnated into theflat-woven fabric, and may therefore tightly adhere thereto.Accordingly, the surface treatment of the woven fabric containingpolyester fiber, which has been necessary in the prior art, is no longernecessary.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing for explaining an apparatus for manufacturing aprepreg for configuring the sliding contact surface-forming material;

FIG. 2 is a perspective view illustrating the prepreg for configuringthe sliding contact surface-forming material;

FIG. 3 is a perspective view illustrating resin bases (prepreg)composing a stack (metal backing);

FIG. 4 is a drawing schematically illustrating an exemplary method ofmanufacturing the flat plate-type multi-layered sliding contactcomponent using the prepreg illustrated in FIG. 2 and the prepregillustrated in FIG. 3;

FIG. 5 is a schematic drawing illustrating a flat plate-typemulti-layered sliding contact component;

FIG. 6 is a drawing schematically illustrating an exemplary method ofmanufacturing a circular cylindrical multi-layered sliding contactcomponent using the prepreg illustrated in FIG. 2;

FIG. 7 is a perspective view illustrating the circular cylindricalmulti-layered sliding contact component;

FIG. 8 is a perspective view illustrating a method of thrust bearingtest;

FIG. 9 is a perspective view illustrating a method of testing journalunder oscillating conditions; and

FIG. 10 is a drawing illustrating an exemplary method of manufacturing aply yarn.

DESCRIPTION OF EMBODIMENTS

The sliding contact surface-forming material, and the multi-layeredsliding contact component using the sliding contact surface-formingmaterial of the present invention will be explained in detail below.

The sliding contact surface-forming material of the present invention isconfigured by a reinforcing base impregnated with a resol-type phenolicresin having PTFE powder dispersed therein, wherein the reinforcing baseis composed of a woven fabric formed by using, respectively as the warpand the weft, a ply yarn which is formed by paralleling at least twostrands of a single twist yarn spun from fluorine-containing resin fiberand a single twist yarn spun from polyester fiber, and by twisting themin the direction opposite to the direction in which the single twistyarns were spun.

In the present invention, PTFE fiber, PFA fiber, FEP fiber, ETFE fiberand so forth may be used as the fluorine-containing resin fiber. Amongthem, PTFE fiber having a good heat resistance (melting point=327° C.)is particularly preferable for applications of the multi-layered slidingcontact component in which heat resistance is required. Thefluorine-containing resin fibers may be formed in both forms of spunyarn and filament yarn, wherein the spun yarn is preferable.

The single twist yarn spun from fluorine-containing resin fiber is ayarn formed by left-twisting (Z-twisting) of filament yarn or spun yarnof at least 400 denier, more preferably spun yarn, at 260 to 300 T/m.

The polyester fiber is preferably obtained generally by polycondensationof a dicarboxylic acid component and a diol component. The carboxylicacid component of polyester is exemplified by terephthalic acid,isophthalic acid, and naphthalene-2,6-dicarboxylic acid; and the diolcomponent of polyester is exemplified by ethylene glycol, hydroquinone,bisphenol A, and biphenyl. Those capable of serving as the both areexemplified by p-hydroxybenzoic acid, and 2-oxy-6-naphthoic acid. Thesingle twist yarn spun from polyester fiber herein is formed byleft-twisting (Z-twisting) of filament yarn or spun yarn, preferablyspun yarn, having a cotton count of at least No. 30 (in denier,approximately 177 denier), at 260 to 300 T/m.

In the present invention, the ply yarn is formed by paralleling at leasttwo strands, wherein one is a single twist yarn composed of a spun yarnor filament yarn spun from fluorine-containing resin fiber, and theother is a single twist yarn composed of a spun yarn or filament yarnspun from polyester fiber, and by twisting them in the direction(S-twisting) opposite to the direction in which the single twist yarnswere spun.

FIG. 10 is a drawing for explaining an exemplary method of manufacturingthe ply yarn. Referring to FIG. 10, a single yarn 80 of fiber “A” istwisted to produce a single twist yarn 100 of fiber “A”. Separately, asingle yarn 120 of fiber “B” is twisted to produce a single twist yarn140 of fiber “B”. The single twist yarn 100 of fiber “A” and the singletwist yarn 140 of fiber “B” are paralleled, and then twisted in thedirection opposite to the direction in which the single twist yarns 100,140 were spun, to thereby form a ply yarn 160.

A woven fabric which serves as the reinforcing base may be formed byweaving the ply yarn used as the warp (vertical yarn) and the weft(horizontal yarn). A flat-woven fabric having a density of 36 to 44ends/inch for the vertical yarn (warp), and a density of 36 to 44picks/inch for the horizontal yarn (weft), may preferably be used as thereinforcing base. Since the flat-woven fabric used as the reinforcingbase allows the fluorine-containing resin fiber and the polyester fiberto expose on at least one surface thereof which serves as the slidingcontact surface, while keeping almost equal areas of exposure, so thatthe flat-woven fabric successfully provides a sliding contactsurface-forming material, improved in the friction-proof and wear-proofcharacteristics, contributed also by low friction properties of the PTFEpowder impregnated into the fabric. Even if the woven fabric ismachined, the fluorine-containing resin fiber and the polyester fiberexpose in nearly equal areas on the surface which serves as the slidingcontact surface, so that the friction-proof and wear-proofcharacteristics of the reinforcing base may be maintained over a longperiod. The woven fabric woven, as the reinforcing base, using the plyyarn as the warp and weft thereof may be thickened. The possibility ofthickening allows machine processing of the sliding contact surface ofthe multi-layered sliding contact component which has, as integrallyprovided to the sliding contact surface thereof, the sliding contactsurface-forming material, the reinforcing base of which is impregnatedwith a specific resol-type phenolic resin having PTFE dispersed therein.Accordingly, dimensional accuracy of the multi-layered sliding contactcomponent may successfully be improved.

An appropriate amount of the reinforcing base composed of the wovenfabric, contained in the sliding contact surface-forming material of thepresent invention, is 35 to 50% by weight. The amount of reinforcingbase less than 35% by weight may fail in fully expressing thefriction-proof and wear-proof characteristics, whereas the amountexceeding 50% by weight may reduce the amount of resol-type phenolicresin described later, and may therefore considerably degrade themoldability.

In the present invention, the resol-type phenolic resin is synthesizedby allowing a phenolic compound containing 50 to 100 mol % of bisphenolA to react with a formaldehyde compound, while being catalyzed by anamine compound. The resol-type phenolic resin preferably has anumber-average molecular weight Mn, measured by GPC, of 500 to 1000, andhas a distribution index Mw/Mn, given as a ratio of weight-averagemolecular weight Mw and number-average molecular weight Mn, of 2.5 to15.

As described in the above, the resol-type phenolic resin used in thepresent invention preferably has a ratio of bisphenol A (C₁₅H₁₆O₂) inthe phenolic compound of 50 to 100 mol %. The ratio herein represents aratio of molarity of bisphenol A relative to the total molarity of allphenolic compounds charged at the start of synthesis.

The thus-synthesized, resol-type phenolic resin preferably has anumber-average molecular weight Mn, measured by GPC, of 500 to 1000, anda distribution index Mw/Mn of molecular weight distribution of 2.5 to15. The resol-type phenolic resin is distinctively increased in theaffinity to the polyester fiber-containing woven fabric. Accordingly,the sliding contact surface-forming material having good adhesivenesswith polyester fiber may be obtained, without subjecting the polyesterfiber to any surface treatment.

The resol-type phenolic resin having a bisphenol A content of less than50 mol % may fail in obtaining a sufficient level of affinity to thepolyester fiber, and may thereby fail in obtaining a sufficient level ofadhesiveness with the polyester fiber-containing woven fabric. Theresol-type phenolic resin also preferably has a number-average molecularweight Mn, measured by GPC, of 500 to 1000, and has a distribution indexMw/Mn of 2.5 to 15. The number-average molecular weight Mn smaller than500 may induce degradation in the mechanical strength despite itsdesirable affinity with the polyester fiber, whereas the number-averagemolecular weight Mn exceeding 1000 may excessively elevates theviscosity of the resol-type phenolic resin, and may make the resindifficult to impregnate into the polyester fiber-containing wovenfabric. The distribution index Mw/Mn of smaller than 2.5 may fail inobtaining a sufficient level of adhesiveness with the polyester fiber,whereas the distribution index Mw/Mn exceeding 15 may make the resindifficult to impregnate into the polyester fiber-containing wovenfabric, similarly to the case where the number-average molecular weightMn exceeds 1000.

Accordingly, the resol-type phenolic resin to be impregnated into thepolyester fiber-containing woven fabric is now successful to ensuresufficient levels of readiness of impregnation and adhesiveness withrespect to the polyester fiber-containing woven fabric, and themechanical strength of the sliding contact surface-forming material, byadjusting the molar ratio of bisphenol A in the phenolic compound, andnumber-average molecular weight Mn and distribution index Mw/Mnmeasurable by GPC, to the above-described ranges.

For the case where the ratio of bisphenol A in the phenolic compound isless than 100 mol %, phenol compound other than bisphenol A is containedas a matter of course. The phenolic compound other than bisphenol A isexemplified by phenol, cresol, ethylphenol, aminophenol, resolcinol,xylenol, butylphenol, trimethylphenol, catechol, and phenylphenol. Amongthem, phenol is preferably used by virtue of its characteristics. Thephenolic compounds other than bisphenol A may be used independently, oras a mixture of two or more species.

The formaldehyde compound is exemplified by formalin, paraformaldehyde,salicylaldehyde, benzaldehyde, and p-hydroxybenzaldehyde. In particular,formalin and paraformaldehyde are preferably used in view of readinessof synthesis. The formaldehyde compounds may be used independently, oras a mixture of two or more species.

The amines used as the catalyst is exemplified by triethylamine,triethanolamine, benzyldimethylamine, and aqueous ammonia. Among them,triethylamine and aqueous ammonia are preferably used in view ofreadiness of synthesis.

The content of resol-type phenolic resin contained in the slidingcontact surface-forming material of the present invention is preferably35 to 50% by weight. The content of resol-type phenolic resin less than35% by weight may adversely affect the moldability (manufacturing) ofthe sliding contact surface-forming material, whereas the contentexceeding 50% by weight may degrade the mechanical strength of thesliding contact surface-forming material.

The PTFE powder to be mixed to the resol-type phenolic resin may beeither of molding powder (abbreviated as “high-molecular-weight PTFE”,hereinafter) for molding, and PTFE (abbreviated as “low-molecular-weightPTFE”, hereinafter) having the molecular weight reduced from that of thehigh-molecular-weight PTFE typically by irradiation. Thelow-molecular-weight PTFE is typically used as an additive, readilycrushable, and highly dispersible.

Specific examples of the high-molecular-weight PTFE include “Teflon(registered trademark) 7-J”, “Teflon (registered trademark) 7A-J”,“Teflon (registered trademark) 70-J”, etc. from Du Pont-MitsuiFluorochemicals Co., Ltd.; “Polyflon M-12 (trade name)” etc. from DaikinIndustries, Ltd.; and “Fluon G163 (trade name)”, “Fluon G190 (tradename)”, etc. from Asahi Glass Co., Ltd.

Specific examples of the low-molecular-weight PTFE include “TLP-10F(trade name)” etc. from Du Pont-Mitsui Fluorochemicals Co., Ltd.;“Lubron L-5 (trade name)” etc. from Daikin Industries, Ltd.; “FluonL150J (trade name)”, “Fluon L169J (trade name)”, etc. from Asahi GlassCo., Ltd.; and “KTL-8N (trade name)”, “KTL-2N (trade name)”, etc. fromKitamura Ltd.

While both of high-molecular-weight PTFE and low-molecular-weight PTFEmay be adoptable to the present invention, powder oflow-molecular-weight PTFE is preferable, in view of uniform dispersionand suppression of void formation when mixed with the resol-typephenolic resin. The average particle size of the PTFE powder ispreferably 1 to 50 μm, and more preferably 1 to 30 μm, in view ofensuring uniform dispersion and preventing voids from being formed.

An appropriate amount of PTFE contained in the sliding contactsurface-forming material is 10 to 30% by weight. The amount of PTFE lessthan 10% by weight may fail in effectively improving the friction-proofand wear-proof characteristics, whereas the amount exceeding 30% byweight may increase the viscosity of resin in the process of molding,may form voids, may reduce adhesiveness of the resol-type phenolicresin, may reduce the strength of the sliding contact surface-formingmaterial or the multi-layered sliding contact component, and may therebyinduce separation between the layers.

As is understood from the explanation in the above, the sliding contactsurface-forming material of the present invention is composed of 35 to50% by weight of reinforcing base which is composed of a woven fabricformed by using, respectively as the warp (vertical yarn) and the weft(horizontal yarn), a ply yarn formed by a single twist yarn spun fromfluorine-containing resin fiber and a single twist yarn spun frompolyester fiber, 10 to 30% by weight of PTFE, and 35 to 50% by weight ofresol-type phenolic resin. The sliding contact surface-forming materialis excellent in all of moldability, mechanical strength, andfriction-proof and wear-proof characteristics.

Next, the sliding contact surface-forming material and the multi-layeredsliding contact component using the sliding contact surface-formingmaterial will be explained referring to the attached drawings whichillustrate preferred examples.

<Sliding Contact Surface-Forming Material>

FIG. 1 is a drawing schematically illustrating an exemplary method ofmanufacturing a prepreg for configuring the sliding contactsurface-forming material. In a manufacturing apparatus illustrated inFIG. 1, a reinforcing base 2 which is composed of a woven fabric formedby using, respectively as the warp (horizontal yarn) and the weft(vertical yarn), a ply yarn composed of a single twist yarn spun fromfluorine-containing resin fiber and a single twist yarn spun frompolyester fiber, preliminarily wound up on an uncoiler 1, is fed withthe aid of a feed roller 3 to a container 5 which contains a mixedliquid 4 composed of PTFE powder and a resol-type phenolic resinvarnish. The mixed liquid 4 is coated on the surface of the reinforcingbase 2, as the reinforcing base 2 is allowed to pass through the mixedliquid 4 retained in the container 5 with the aid of guide rollers 6 and7 provided in the container 5. The reinforcing base 2 coated with themixed liquid 4 is fed by a feed roller 8 to compression rolls 9 and 10,where the mixed liquid 4 coated on the surface of the reinforcing base 2is allowed to impregnate deep into voids in the fiber texture by thecompression rolls 9 and 10. In the process of vaporization of thesolvent, in a drying oven 11, out from the reinforcing base 2 coated andimpregnated with the mixed liquid 4, also a reaction of the resol-typephenolic resin varnish proceeds, and thereby a moldable prepreg (resinbase) 12 for configuring the sliding contact surface-forming material ismanufactured. FIG. 2 is a perspective view illustrating the square-cutprepreg 12 for configuring the sliding contact surface-forming material.

Solid content of the resol-type phenolic resin 4 prepared by dissolvingthe resol-type phenolic resin into a volatile solvent is approximately30 to 65% by weight of the whole resin varnish, viscosity of the resinvarnish is preferably 800 to 5000 cP, and particularly preferably 1000to 4000 cP.

<Flat Plate-Type Multi-layered Sliding Contact Component>

A multi-layered sliding contact component 13 formed by using the prepreg12 for configuring the sliding contact surface-forming material will beexplained referring to FIG. 3 to FIG. 5. A metal backing 14 of themulti-layered sliding contact component 13 is manufactured using amanufacturing apparatus similar to that illustrated in FIG. 1 used inthe method of manufacturing the prepreg 12 for configuring the slidingcontact surface-forming material, and by a similar method ofmanufacturing. More specifically, a woven fabric 15 woven using anorganic fiber or an inorganic fiber and wound up on the uncoiler 1 isfed with the aid of the feed roller 3 to the container 5 which containsa resol-type phenolic resin varnish 16, and allowed to pass through theresol-type phenolic resin varnish contained in the container 5 with theaid of the guide rollers 6 and 7 provided in the container 5. The resinvarnish is thus coated on the surface of the woven fabric 15. The wovenfabric 15 coated with the resin varnish is then fed by the feed roller 8to the compression rolls 9 and 10, where the resin varnish isimpregnated into the woven fabric 15. In the process of vaporization ofthe solvent, in the drying oven 11, out from the woven fabric 15, also areaction of the resin varnish proceeds, and thereby a moldable prepreg(resin base) 17 for configuring the metal backing 14 is manufactured.FIG. 3 is a perspective view illustrating a plurality of square-cutprepregs 17 for configuring the metal backing.

Reinforcing fiber woven fabric adoptable to the metal backing 14 may bean inorganic fiber woven fabric such as glass fiber woven fabric, andcarbon fiber woven fabric; or an organic fiber woven fabric such asaramid resin fiber woven fabric (copolyparaphenylene-3,4′-oxydiphenyleneterephthalamide resin fiber woven fabric), each of which isappropriately selectable depending on applications of the multi-layeredsliding contact component, proceeded under dry frictional conditions,underwater frictional conditions, boundary frictional conditions and soforth.

As illustrated in FIG. 3, a necessary number of sheets of the prepreg 17for configuring the metal backing 14, having been square-cut so as toensure a desired area, are prepared, where the number of sheets isdetermined so as to obtain a desired final thickness. On the other hand,at least one sheet of the prepreg 12 for configuring the sliding contactsurface-forming material, having been square-cut similarly to theprepreg 17 for configuring the metal backingh 14, is prepared. Next, asillustrated in FIG. 4, a predetermined number of sheets of prepreg 17for configuring the metal backing are stacked in a square recess 19 of adie 18 of a heat pressing machine, and the prepregs 12 for configuringthe sliding contact surface-forming material are placed thereon. Thestack is heated to 140 to 160° C. in the die 18, and pressed under aload of 4.9 to 7 MPa in the direction of stacking using a ram 20, tothereby obtain a square laminated mold. The stacked prepregs 12 forconfiguring the sliding contact surface-forming material and theprepregs 17 for configuring the metal backing are bonded and fused witheach other. The thus-obtained laminated mold is machined, to therebygive a flat plate-type multi-layered sliding contact component 13illustrated in FIG. 5. The flat plate-type multi-layered sliding contactcomponent 13 manufactured as described in the above has the metalbacking 14 composed of a stack of inorganic fiber woven fabric ororganic fiber woven fabric, and a slipping layer 21 composed of theprepreg 12 for configuring the sliding contact surface-forming materialand integrally bonded to one surface of the metal backing 14. In themulti-layered sliding contact component 13, the slipping layer 21, whichis composed of the prepreg 12 for configuring the sliding contactsurface-forming material and is integrally bonded on the metal backing14, is not only excellent in the friction-proof and wear-proofcharacteristics, but also improved in the load resistance. In addition,since the amount of swelling in moist atmosphere such as in oil or wateris extremely small, so that the multi-layered sliding contact component13 is adoptable to a wide variety of applications proceeded under dryfrictional conditions, boundary frictional conditions, and waterlubricating conditions.

<Circular Cylindrical Multi-Layered Sliding Contact Component>

FIG. 6 and FIG. 7 are drawings illustrating an exemplary method ofmanufacturing of the circular cylindrical multi-layered sliding contactcomponent, having the sliding contact surface-forming materialintegrally bonded to the sliding contact surface (inner circumferentialsurface). The circular cylindrical multi-layered sliding contactcomponent may be manufactured by rolled forming using a rolled formingmachine. A rolled forming machine illustrated in FIG. 6 generally hastwo heat rollers 22 and one pressure roller 23 respectively located atthe apexes of triangle, and a core die 24 located at the center of thetriangle, configured to form the circular cylindrical multi-layeredsliding contact component while wrapping the prepregs 12 and 17 aroundthe core die 24 and rotating the core die 24 in one direction, underheating and pressurizing by the three rollers 22, 22 and 23.

In the rolled forming machine illustrated in FIG. 6, rolled forming isconducted so that the prepreg 12 for configuring the sliding contactsurface-forming material, slit to a predetermined width, is wrapped atleast one turn around the outer circumferential surface of the core die24 preliminarily heated to 120 to 200° C., the prepreg 17 forconfiguring the metal backing is fed further on the outercircumferential surface thereof from the feeding roll 25 via the heatrollers 22 heated to 120 to 200° C., and then wound to a desired finalthickness (diameter) under a pressure of 2 to 6 MPa with the aid of thepressure roller 23. The thus-molded circular cylindrical laminated mold26, as held around the core die 24, is cured under heating in a heatingoven conditioned at an ambient temperature of 120 to 180° C., thencooled, the core die 24 is drawn out, to thereby obtain the circularcylindrical laminated mold 26. Next, the thus-manufactured circularcylindrical laminated mold 26 is machined to form a circular cylindricalmulti-layered sliding contact component 27 having a desired dimension asillustrated in FIG. 7. The thus-formed circular cylindricalmulti-layered sliding contact component 27 has a slipping layer 29composed of the prepreg 12 for configuring the sliding contactsurface-forming material, which is integrally bonded to the innersurface of the circular cylindrical metal backing 28. The innercircumferential surface of the slipping layer 29 serves as the slidingcontact surface. The circular cylindrical multi-layered sliding contactcomponent 27 is excellent in the friction-proof and wear-proofcharacteristics, improved in the load resistance, causative of anextremely small amount of swelling when used in a moist atmosphere suchas in oil or water, and is therefore applicable to a wide variety ofapplications proceeded under dry frictional conditions, boundaryfrictional conditions, and water lubricating conditions.

EXAMPLES

The present invention will be detailed below referring to Examples. Itis to be understood that the present invention is not limited toExamples below, without departing from the spirit thereof.

<Flat Plate-Type Multi-Layered Sliding Contact Component>

Examples 1 to 3

(Reinforcing Base for Sliding Contact Surface-Forming Material)

A single twist yarn formed by left-twisting (Z-twisting) at 280 T/m of a400-denier spun yarn spun from PTFE fiber used as thefluorine-containing resin fiber, and a single twist yarn formed byleft-twisting (Z-twisting) at 280 T/m of a No. 30-cotton-count spun yarnspun from polyester fiber, were prepared. One each of the single twistyarns were paralleled, and these two single twist yarns were twisted at275 T/m in the direction (S-direction) opposite to the direction(Z-direction) in which the single twist yarns were spun, to form a plyyarn. Using the ply yarn as the warp (vertical yarn) and the weft(horizontal yarn), a flat-woven fabric having a density of 40 picks/inchfor the horizontal yarn, and 40 ends/inch for the vertical yarn wasproduced. The flat-woven fabric was used later as a reinforcing base forthe sliding contact surface-forming material.

(Resol-Type Phenolic Resin)

Into a separable flask equipped with a stirrer, a thermometer and acondenser tube, 300 g of bisphenol A and 192 g of a 37% aqueousformaldehyde solution were placed, 9 g of a 25% aqueous ammonia solutionwas added under stirring, the content was heated under normal pressureup to 90° C., and a condensation reaction was allowed to proceed for 2.5hours. The content was then heated to 80° C. under a reduced pressure of0.015 MPa for dehydration. The content was then added with 64 g ofmethanol, heated to 85° C. under normal pressure, a condensationreaction was allowed to proceed for 4 hours, the content wasconcentrated, diluted with methanol so as to adjust the resin solidcontent to 60% by weight, to thereby produce a resol-type phenolic resin(varnish with a solid content of 60% by weight). In Examples 1 to 3, themolar ratio of bisphenol A in the phenolic compound used herein was 100mol %. By GPC measurement, the obtained resol-type phenolic resin wasfound to have a number-average molecular weight Mn of 900, and adistribution index Mw/Mn of molecular weight distribution of 5.6.

A low-molecular-weight PTFE powder (from Kitamura Ltd. KTL-2N (tradename)) was used as PTFE, a predetermined amount of which for eachExample was mixed with, and dispersed into the resol-type phenolic resinvarnish, to thereby prepare a mixed liquid of the resin varnish and thelow-molecular-weight PTFE powder.

Now by using the manufacturing apparatus illustrated in FIG. 1, thereinforcing base 2, composed of a flat-woven fabric and preliminarilywound up on the uncoiler 1, was fed with the aid of the feed roller 3 tothe container 5 which contains the mixed liquid 4. The mixed liquid 4was coated on the surface of the reinforcing base 2, as the reinforcingbase 2 was allowed to pass through the mixed liquid 4 retained in thecontainer 5 with the aid of guide rollers 6 and 7 provided in thecontainer 5. The reinforcing base 2 coated with the mixed liquid 4 wasfed by thea feed roller 8 to the compression rolls 9 and 10, where themixed liquid 4 coated on the surface of the reinforcing base 2 wasallowed to impregnate deep into voids in the fiber texture by thecompression rolls 9 and 10. The reinforcing base 2 impregnated with themixed liquid 4 was then fed to the drying oven 11, where the solvent wasvaporized off, and the mixed liquid 4 was allowed to proceed a reaction,to thereby give the prepregs (resin base) 12 for configuring the slidingcontact surface-forming material having the compositions listed below:

(Example 1) reinforcing base (flat-woven fabric)=43.5% by weight,PTFE=13% by weight, and resol-type phenolic resin=43.5% by weight;

(Example 2) reinforcing base (ditto)=40% by weight, PTFE=20% by weight,and resol-type phenolic resin=40% by weight; and

(Example 3) reinforcing base (ditto)=37% by weight, PTFE=26% by weight,and resol-type phenolic resin=37% by weight.

(Metal Backing)

A glass fiber flat-woven fabric, woven using a glass fiber single yarnspun from 100 single fibers (monofilaments) each having 5-μm diameter,and having a density of 65 picks/inch for the weft (horizontal yarn) anda density of 65 ends/inch for the warp (vertical yarn), was used as thereinforcing fiber woven fabric, and the resol-type phenolic resin(varnish with a solid content of 60% by weight) same as that describedin the above was used as a thermosetting synthetic resin. Using themanufacturing apparatus illustrated in FIG. 1, the glass fiberflat-woven fabric 15 preliminarily wound up on the uncoiler 1, was fedwith the aid of the feed roller 3 to the container 5 which contains theresol-type phenolic resin varnish. The resin varnish was coated on thesurface of the flat-woven fabric 15, as the flat-woven fabric 15 wasallowed to pass through the resol-type phenolic resin varnish 16retained in the container 5 with the aid of the guide rollers 6 and 7provided in the container 5. The woven fabric 15 coated with the resinvarnish was fed by the feed roller 8 to the compression rolls 9 and 10,where the resin varnish was impregnated into the woven fabric 15 by thecompression rolls 9 and 10. The flat-woven fabric 15 was then fed to thedrying oven 11, where the solvent was vaporized off, and the resinvarnish was allowed to proceed a reaction, to thereby give the moldableprepregs 17 for configuring the metal backing, having a glass fiberflat-woven fabric content of 40% by weight, and a resol-type phenolicresin content of 60% by weight.

(Multi-Layered Sliding Contact Component)

The prepreg for configuring the metal backing was cut into 31-mm squaresheets, and ten sheets were stacked in the square recess 19 of the die18 of the heat pressing machine illustrated in FIG. 4. On the otherhand, each of the prepregs for configuring the sliding contactsurface-forming material, obtained in Example 1 to Example 3, was cutinto 31-mm square sheets, and three of the sheets were stacked on theprepregs for configuring the metal backing preliminarily stacked in therecess 19 of the die, heated in the die 18 at 160° C. for 10 minutes,pressed in the direction of stacking at a pressure of 7 MPa, to therebyobtain a square laminated mold. The mold was machined, to thereby give aflat plate-type multi-layered sliding contact component 13 having anedge length of 30 mm and a thickness of 5 mm, composed of the metalbacking 14, and the slipping layer 21 composed of the sliding contactsurface-forming material integrally bonded to the surface of the metalbacking 14.

Examples 4 to 6

(Reinforcing Base for Configuring Sliding Contact Surface-FormingMaterial)

Single twist yarns formed by left-twisting (Z-twisting) at 300 T/m of400-denir spun yarn spun respectively from FEP fiber (Example 4), PFAfiber (Example 5), and ETFE fiber (Example 6) as the fluorine-containingresin fiber, and a single twist yarn formed by left-twisting(Z-twisting) at 300 T/m of polyester fiber of No. 30 cotton count, wereprepared. One each of the single twist yarns were paralleled, and thentwisted (S-twisting) at 295 T/m in the direction (S-direction) oppositeto the direction (Z-direction) in which the single twist yarns werespun, to form a ply yarn. Using the ply yarn as the warp (vertical yarn)and the weft (horizontal yarn), a flat-woven fabric having a density of40 picks/inch for the horizontal yarn, and 40 ends/inch for the verticalyarn was produced. The flat-woven fabric was used later as a reinforcingbase 2 for configuring the sliding contact surface-forming material.

(Resol-Type Phenolic Resin)

In a separable flask similar to that used in the above-describedExamples, 160 g of bisphenol A and 79 g of a 37% aqueous formaldehydesolution were placed, 1.3 g of triethylamine was added under stirring,the content was heated under normal pressure, and allowed to proceed acondensation reaction under a reflux condition at 100° C. for one hour.The content was then cooled, and 32 g of phenol, 30 g of a 37% aqueousformaldehyde solution, and 0.3 g of triethylamine were added. Thecontent was heated under normal pressure, and allowed to proceed acondensation reaction under a reflux condition at 100° C. for 2 hour,and then heated to 80° C. under a reduced pressure of 0.015 MPa fordehydration. The content was then added with 24 g of methanol, heated to90° C. under normal pressure, a condensation reaction was allowed toproceed for 4 hours, the content was concentrated, diluted with methanolso as to adjust the resin solid content to 60% by weight, to therebyproduce a resol-type phenolic resin (varnish with a solid content of 60%by weight). In Examples 4 to 6, the molar ratio of bisphenol A in thephenolic compound used herein was 67.4 mol %. By GPC measurement, theobtained resol-type phenolic resin was found to have a number-averagemolecular weight Mn of 720, and a distribution index Mw/Mn of molecularweight distribution of 14.3.

A low-molecular-weight PTFE powder (same as that used in theabove-described Examples) was used as PTFE, a predetermined amount ofwhich for each Example was mixed with, and dispersed into the resol-typephenolic resin varnish, to thereby prepare a mixed liquid of the resinvarnish and the low-molecular-weight PTFE powder.

Similarly to the above-described Examples, using the manufacturingapparatus illustrated in FIG. 1, the reinforcing base 2, composed of aflat-woven fabric and preliminarily wound up on the uncoiler 1, was fedwith the aid of the feed roller 3 to the container 5 which contains themixed liquid 4. The mixed liquid 4 was coated on the surface of thereinforcing base 2, as the reinforcing base 2 was allowed to passthrough the mixed liquid 4 retained in the container 5 with the aid ofthe guide rollers 6 and 7 provided in the container 5. The reinforcingbase 2 coated with the mixed liquid 4 was fed by the feed roller 8 tothe compression rolls 9 and 10, where the mixed liquid 4 coated on thesurface of the reinforcing base 2 was allowed to impregnate deep intovoids in the fiber texture by the compression rolls 9 and 10. Thereinforcing base 2 impregnated with the mixed liquid 4 was then fed tothe drying oven 11, where the solvent was vaporized off, and the mixedliquid 4 was allowed to proceed a reaction, to thereby give the prepregs(resin base) for configuring the sliding contact surface-formingmaterial having the compositions listed below:

(Example 4) reinforcing base (flat-woven fabric)=43.5% by weight,PTFE=13% by weight, and resol-type phenolic resin=43.5% by weight;

(Example 5) reinforcing base (ditto)=40% by weight, PTFE=20% by weight,and resol-type phenolic resin=40% by weight; and

(Example 6) reinforcing base (ditto)=37% by weight, PTFE=26% by weight,and resol-type phenolic resin=37% by weight.

(Metal Backing)

The metal backing was manufactured by using the moldable prepreg forconfiguring the metal backing, having a glass fiber flat-woven fabriccontent of 40% by weight, and a resol-type phenolic resin content of 60%by weight, which is the same as that used in the above-describedExamples.

(Multi-Layered Sliding Contact Component)

The multi-layered sliding contact component having an edge length of 30mm and a thickness of 5 mm, composed of the metal backing, and theslipping layer composed of the sliding contact surface-forming materialintegrally bonded to the surface of the metal backing, was manufacturedsimilarly as described in the aforementioned Examples.

(Circular Cylindrical Multi-Layered Sliding Contact Component)

Examples 7 to 9

In the rolled forming machine illustrated in FIG. 6, rolled forming wasconducted so that the prepreg 12 for configuring the sliding contactsurface-forming material, slit into 51-mm wide, same as that describedin each of Examples 1 to 3, was wrapped three turns around the outercircumferential surface of the core die 24 having an outer diameter of60 mm and preliminarily heated to 150° C., the prepreg 17 forconfiguring the metal backing, same as that described in theaforementioned Examples, was fed further on the outer circumferentialsurface thereof from the feeding roll 25 via the heat rollers 22 heatedto 150° C., and then wound 15 turns under a pressure of 5 MPa with theaid of the pressure roller 23. The thus-molded circular cylindricallaminated mold 26, as held around the core die 24, was cured underheating in a heating oven conditioned at an ambient temperature of 150°C., then cooled, the core die 24 was drawn out, to thereby obtain thecircular cylindrical laminated mold 26. Next, the thus-manufacturedcircular cylindrical laminated mold 26 was machined to form a circularcylindrical multi-layered sliding contact component 27 having an innerdiameter of 60 mm, an outer diameter of 75 mm, and a length of 50 mm, asillustrated in FIG. 7. The circular cylindrical multi-layered slidingcontact component 27 of Example 7 was given by using the sliding contactsurface-forming material same as that used in Example 1, the circularcylindrical multi-layered sliding contact component 27 of Example 8 wasgiven by using the sliding contact surface-forming material same as thatused in Example 2, and the circular cylindrical multi-layered slidingcontact component 27 of Example 9 was given by using the sliding contactsurface-forming material same as that used in Example 3.

(Circular Cylindrical Multi-Layered Sliding Contact Component)

Examples 10 to 12

In the rolled forming machine illustrated in FIG. 6, rolled forming wasconducted so that the prepreg 12 for configuring the sliding contactsurface-forming material, slit into 51-mm wide, same as that describedin each of Examples 4 to 6, was wrapped three turns around the outercircumferential surface of the core die 24 having an outer diameter of60 mm and preliminarily heated to 150° C., the prepreg 17 forconfiguring the metal backing, same as that described in Examples, wasfed further on the outer circumferential surface thereof from thefeeding roll 25 via the heat rollers 21 heated to 150° C., and thenwound 15 turns under a pressure of 5 MPa with the aid of the pressureroller 23. The thus-molded circular cylindrical laminated mold 26, asheld around the core die 24, was cured under heating in a heating ovenconditioned at an ambient temperature of 150° C., then cooled, the coredie 24 was drawn out, to thereby obtain the circular cylindricallaminated mold 26. Next, the thus-manufactured circular cylindricallaminated mold 26 was machined to form a circular cylindricalmulti-layered sliding contact component 27 having an inner diameter of60 mm, an outer diameter of 75 mm, and a length of 50 mm, as illustratedin FIG. 7. The circular cylindrical multi-layered sliding contactcomponent 27 of Example 10 was given by using the sliding contactsurface-forming material same as that used in Example 4, the circularcylindrical multi-layered sliding contact component 27 of Example 11 wasgiven by using the sliding contact surface-forming material same as thatused in Example 5, and the circular cylindrical multi-layered slidingcontact component 27 of Example 12 was given by using the slidingcontact surface-forming material same as that used in Example 6.

<Flat Plate-Type Multi-Layered Sliding Contact Component>

Comparative Examples 1 to 3

The reinforcing fiber woven fabric used herein was a flat-woven fabricwhich was woven by using a polyester fiber spun yarn of No. 20 cottoncount as the warp (vertical yarn) and the weft (horizontal yarn), with adensity of 43 ends/inch for the warp, and a density of 42 picks/inch forthe weft. By using the resol-type phenolic resin containing the PTFEpowder same as that described in Examples 1 to 3, the prepregs forconfiguring the sliding contact surface-forming material having thecompositions listed below were manufactured:

(Comparative Example 1) reinforcing base (flat-woven fabric)=43.5% byweight, PTFE=13% by weight, and resol-type phenolic resin=43.5% byweight;

(Comparative Example 2) reinforcing base (ditto)=40% by weight, PTFE=20%by weight, and resol-type phenolic resin=40% by weight; and

(Comparative Example 3) reinforcing base (ditto)=37% by weight, PTFE=26%by weight, and resol-type phenolic resin=37% by weight.

The moldable prepreg 16 for configuring the metal backing, composed of40% by weight of glass fiber flat-woven fabric, and 60% by weight ofresol-type phenolic resin, same as that described in Example 1 toExample 3, were used as the prepreg for configuring the metal backing.The prepreg 17 for configuring the metal backing was cut into 31-mmsquare sheets, and ten sheets were stacked in the square recess 19 ofthe die 18 of the heat pressing machine illustrated in FIG. 4. On theother hand, the prepregs 12 for configuring the sliding contactsurface-forming material, obtained in Comparative Example 1 was cut into31-mm square sheets, and three of the sheets were stacked on theprepregs 17 for configuring the metal backing preliminarily stacked inthe recess 19 of the die, heated in the die 18 at 160° C. for 10minutes, pressed in the direction of stacking at a pressure of 7 MPa, tothereby obtain a square laminated mold. The mold was machined, tothereby give a multi-layered sliding contact component 13 having an edgelength of 30 mm and a thickness of 5 mm, composed of the metal backing14, and the slipping layer 21 composed of the sliding contactsurface-forming material integrally bonded to the surface of the metalbacking 14.

<Circular Cylindrical Multi-Layered Sliding Contact Component>

Comparative Examples 4 to 6

In the rolled forming machine illustrated in FIG. 6, rolled forming wasconducted so that the prepreg 12 for configuring the sliding contactsurface-forming material, slit into 51-mm wide, same as that describedin each of Comparative Examples 1 to 3, was wrapped three turns aroundthe outer circumferential surface of the core die 24 having an outerdiameter of 60 mm and preliminarily heated to 150° C., the prepreg 16for configuring the metal backing, same as that described in Examples 1to 3, was fed further on the outer circumferential surface thereof fromthe feeding roll 25 via the heat rollers 22 heated to 150° C., and thenwound 15 turns under a pressure of 5 MPa with the aid of the pressureroller 23. The thus-molded circular cylindrical laminated mold 26, asheld around the core die 24, was cured under heating in a heating ovenconditioned at an ambient temperature of 150° C., then cooled, the coredie 24 was drawn out, to thereby obtain the circular cylindricallaminated mold 26. Next, the thus-manufactured circular cylindricallaminated mold 26 was machined to form a circular cylindricalmulti-layered sliding contact component 27 having an inner diameter of60 mm, an outer diameter of 75 mm, and a length of 50 mm, as illustratedin FIG. 7. The circular cylindrical multi-layered sliding contactcomponent 27 of Comparative Example 4 was given by using the slidingcontact surface-forming material same as that used in ComparativeExample 1, the circular cylindrical multi-layered sliding contactcomponent 27 of Comparative Example 5 was given by using the slidingcontact surface-forming material same as that used in ComparativeExample 2, and the circular cylindrical multi-layered sliding contactcomponent 27 of Comparative Example 6 was given by using the slidingcontact surface-forming material same as that used in ComparativeExample 3.

Next, results of experiments on the friction-proof and wear-proofcharacteristics, and the amount of swelling (%) in water, of themulti-layered sliding contact components obtained in Examples andComparative Examples will be explained.

Friction-Proof and Wear-Proof Characteristics of Flat plate-typeMulti-Layered Sliding Contact Component in Examples 1 to 6 andComparative Examples 1 to 3

(1) Thrust Bearing Test

The friction coefficient and amount of wear were measured according tothe test conditions listed in Table 1. The amount of wear wasrepresented by the amount of dimensional change observed after the30-hour testing.

TABLE 1 Surface pressure 29.4 MPa (300 kgf/cm²) Sliding velocity 2 m/minTest period 30 hours Material of opposing austenitic stainless steel(SUS304) member Environment/Atmosphere air Lubrication (1) none (dry)(2) greased on sliding contact surface Test method As illustrated inFIG. 8, a flat plate-type bearing test piece (multi-layered slidingcontact component) 13 was fixed, an opposing circular cylinder 30 wasallowed to rotate in the direction of arrow B, on the flat plate-typebearing test piece 13 (from the direction of arrow “A”) while applying apredetermined load to the surface thereof, and the friction coefficientbetween the flat plate-type bearing test piece 13 and the circularcylinder 30, and the amount the wear (mm) of the flat plate-type bearingtest piece 13 after the elapse of 30 hours were measured.

Friction-Proof and Wear-Proof Characteristics of Circular CylindricalMulti-Layered Sliding Contact Components in Examples 7 to 12 andComparative Examples 4 to 6

(1) Oscillating Test For Journal

The friction coefficient and amount of wear were measured according tothe test conditions listed in Tables 2 and 3. The amount of wear wasrepresented by the amount of dimensional change observed after the100-hour testing.

TABLE 2 Surface pressure 29.4 N/mm² (300 kgf/cm²) Sliding velocity 0.008m/s (0.50 m/min) Oscillation speed 120 cpm Oscillation angle 4° (±2°)Environment/Atmosphere (1) in air (2) in clean water Lubrication noneTest method As illustrated in FIG. 9, a circular cylindrical bearingtest piece (circular cylindrical multi- layered sliding contactcomponent) 27 was fixed under load, an opposing rotating shaft 31 wasallowed to rotate under oscillation at a constant sliding velocity, thenthe friction coefficient between the circular cylindrical bearing testpiece 27 and the rotating shaft 31, and the amount of wear (mm) on theinner circumferential surface (sliding contact surface) of the circularcylindrical bearing test piece 27 after the elapse of 100 hours weremeasured.

TABLE 3 Surface pressure 29.4 N/mm² (300 kgf/cm²) Sliding velocity 0.012m/s (1.13 m/min) Oscillation speed 12 cpm Oscillation angle 90° (±45°)Environment/Atmosphere in air Lubrication none Test method Same as thetest method described in Table 2.

<Test Method for Amount of Swelling>

The test pieces were immersed in water at 20° C. for 120 days, and thentaken out for measurement of rate of dimensional change.

<Results>

Results of test on the friction and wear, and on the amount of swellingare shown in Table 4 to Table 6. In Table 4 to Table 6, thenumber-average molecular weight Mn and distribution index Mw/Mn of theresol-type phenolic resin were measured by GPC, and the values wereestimated based on a standard curve prepared by using polystyrene as astandard substance. Measurement instruments are as follow:

-   GPC analyzer: HLC-8120 from Tosoh Corporation;-   Column: TSK gel G3000HXL [exclusion limit molecular weight    (polystyrene-based) 1×10³]×1, followed by TSK gel G2000HXL    [exclusion limit molecular weight (polystyrene-based) 1×10⁴]×2, from    Tosoh Corporation; and-   Detector: UV-8020 from Tosoh Corporation

TABLE 4 Flat plate-type Example multi-layered sliding contact component1 2 3 4 5 6 Sliding contact Reinforcing base 43.5 40 37 43.5 40 37surface- (fluorine-containing resin PTFE FEP PFA ETFE forming fiber andpolyester fiber) material PTFE 13 20 26 13 20 26 Resol-type phenolicresin 43.5 40 37 43.5 40 37 Ratio of bisphenol A (mol %) 100 67.4Molecular weight Mn 900 720 Distribution Mw/Mn 5.6 14.3 Friction-proof,Thrust bearing Friction 0.08 0.07 0.06 0.09 0.08 0.08 wear-proof testcoefficient characteristics Lubrication Amount of 0.08 0.09 0.09 0.090.09 0.09 (dry) wear (mm) Thrust bearing Friction 0.06 0.06 0.05 0.060.07 0.07 test coefficient Lubrication Amount of 0.05 0.04 0.04 0.060.06 0.07 (greased) wear (mm) Amount of Rate of change 0.12 0.10 0.120.12 0.10 0.13 swelling in length (%) Rate of change 0.54 0.52 0.56 0.520.54 0.50 in thickness (%)

TABLE 5 Flat plate-type Comparative Example multi-layered slidingcontact component 1 2 3 Sliding contact Reinforcing base (polyesterfiber) 43.5 40 37 surface-forming PTFE 13 20 26 material Resol-typephenolic resin 43.5 40 37 Ratio of bisphenol A (mol %) 100 Molecularweight Mn 900 Distribution Mw/Mn 5.6 Friction-proof, Thrust bearing testFriction coefficient 0.13 0.12 0.10 wear-proof Lubrication (dry) Amountof wear (mm) 0.08 0.09 0.10 characteristics Thrust bearing test Frictioncoefficient 0.08 0.06 0.07 Lubrication (greased) Amount of wear (mm)0.03 0.03 0.04 Amount of swelling Rate of change in length (%) 0.18 0.190.18 Rate of change in thickness (%) 0.60 0.58 0.62

TABLE 6 Circular cylindrical Example multi-layered sliding contactcomponent 7 8 9 10 11 12 Sliding Reinforcing base 43.5 40 37 43.5 40 37contact (fluorine-containing resin PTFE FEP PFA ETFE surface- fiber andpolyester fiber) forming PTFE 13 20 26 13 20 26 material Resol-typephenolic resin 43.5 40 37 43.5 40 37 Ratio of bisphenol A (mol %) 10067.4 Molecular weight Mn 900 720 Distribution Mw/Mn 5.6 14.3 Friction-Oscillation test for Friction 0.07 0.07 0.06 0.08 0.08 0.08 proof,journal coefficient wear- (in air: angle of Amount of 0.02 0.03 0.030.03 0.03 0.03 proof oscillation = 4°) wear (mm) character- Oscillationtest for Friction 0.08 0.08 0.08 0.08 0.08 0.09 istics journal (in cleancoefficient water: angle of Amount of 0.01 0.01 0.01 0.02 0.02 0.03oscillation = 4°) wear (mm) Oscillation test for Friction 0.08 0.07 0.070.08 0.07 0.07 journal coefficient (in air: angle of Amount of 0.04 0.050.05 0.04 0.05 0.05 oscillation = 90°) wear (mm) Amount of Rate ofchange in inner 0.12 0.12 0.13 0.13 0.12 0.13 swelling diameter (%) Rateof change in outer 0.28 0.28 0.30 0.30 0.28 0.32 diameter (%) Rate ofchange in length 0.23 0.25 0.25 0.26 0.25 0.26 (%)

TABLE 7 Circular cylindrical Comparative Example multi-layered slidingcontact component 4 5 6 Sliding contact Reinforcing base (polyesterresin fiber) 43.5 40 37 surface-forming PTFE 13 20 26 materialResol-type phenolic resin 43.5 40 37 Ratio of bisphenol A (mol %) 100Molecular weight Mn 900 Distribution Mw/Mn 5.6 Friction-proof,Oscillation test for journal Friction coefficient 0.11 0.12 0.10wear-proof (in air: angle of Amount of wear (mm) 0.05 0.09 0.10characteristics oscillation = 4°) Oscillation test for journal Frictioncoefficient 0.08 0.06 0.07 (in clean water: angle of Amount of wear (mm)0.03 0.03 0.04 oscillation = 4°) Oscillation test for journal Frictioncoefficient 0.14 0.12 0.12 (in air: angle of Amount of wear (mm) 0.610.65 0.72 oscillation = 90°) Amount of swelling Rate of change in innerdiameter (%) 0.12 0.13 0.13 Rate of change in outer diameter (%) 0.280.30 0.30 Rate of change in length (%) 0.25 0.28 0.26

The molar ratio of bisphenol A shown in Table 4 to Table 7 werecalculated by the equation below:

molar ratio=(molarity of bisphenol A as charged/total molarity ofphenolic compounds as charged)×100 (mol %).

It is understood from the test results, particularly from comparison ofthe friction-proof and wear-proof characteristics under journaloscillating conditions shown in Table 6 and Table 7, that themulti-layered sliding contact components of Examples 7 to 12 were foundto show smaller friction coefficients and improved wear resistance, ascompared with the conventional multi-layered sliding contact componentsof Comparative Examples 4 to 6. In particular in the test at an angle ofoscillation of journal of) 90° (±45°), the multi-layered sliding contactcomponents of Examples 7 to 12 were found to be largely improved in thewear resistance, as compared with the conventional multi-layered slidingcontact components of Comparative Examples 4 to 6. The multi-layeredsliding contact components in Examples and Comparative Examples showedalmost equivalent amounts of swelling.

INDUSTRIAL APPLICABILITY

As described in the above, the reinforcing base, which configures thesliding contact surface-forming material of the present invention, andis composed of a woven fabric formed by using, respectively as the warpand the weft, a ply yarn formed by paralleling at least two strands of asingle twist yarn spun from fluorine-containing resin fiber and a singletwist yarn spun from polyester fiber, and by twisting them in thedirection opposite to the direction in which the single twist yarns werespun, allows the fluorine-containing resin fiber and the polyester fiberto expose on at least one surface thereof which serves as the slidingcontact surface, while keeping almost equal areas of exposure. Thepresent invention therefore successfully provides a sliding contactsurface-forming material, improved in the friction-proof and wear-proofcharacteristics contributed by low friction properties of the PTFEpowder impregnated into the woven fabric. The multi-layered slidingcontact component, which has such sliding contact surface-formingmaterial so as to configure the sliding contact surface, has excellentfriction-proof and wear-proof characteristics, high rigidity, andexcellent mechanical strength. In addition, since the multi-layeredsliding contact component shows an extremely small amount of swelling inmoist atmosphere such as underwater, so that dimensional changesascribable the swelling will be extremely small, and this makes thecomponent adoptable to a wide variety of applications proceeded underdry frictional conditions, grease lubricating conditions, and waterlubricating conditions.

EXPLANATION OF THE MARKS

-   2 reinforcing base-   12 prepreg for configuring the sliding contact surface-forming    material-   13 flat plate-type multi-layered sliding contact component-   14 metal backing-   17 prepreg for configuring the metal backing-   21 slipping layer-   27 circular cylindrical multi-layered sliding contact component

1. A method of minimizing friction between two surfaces during relativemovement therebetween in a moist environment, said method comprising thesteps of: placing a slide bearing between said surfaces, placing saidsurfaces in said moist environment, and moving said surfaces relative toone another in said moist environment, wherein the slide bearingcomprises a sliding contact surface-forming material comprising areinforcing base impregnated with a resol phenolic resin havingpolytetrafluoroethylene resin dispersed therein, the reinforcing basecomprising a woven fabric formed by using, respectively as each of thewarp and the weft, a ply yarn which is formed by paralleling at leasttwo strands of: a single twist yarn spun from fluorine-containing resinfiber, and a single twist yarn spun from polyester fiber, and bytwisting them in a direction opposite to the direction in which thesingle twist yarns were spun; and wherein the reinforcing base is aflat-woven fabric having a density of 36 to 44 ends/inch for the warp(vertical yarn), and 36 to 44 picks/inch for the weft (horizontal yarn),wherein the single twist yarn spun from fluorine-containing resin fiberis a yarn of at least 400 denier, wherein the single twist yarn spunfrom polyester fiber has at least No. 30 cotton count, wherein eachsingle twist yarn has a twist count of 260 to 300 T/m, wherein the plyyarn has a twist count of 255 to 295 T/m, and wherein the slidingcontact surface-forming material contains 37 to 43.5% by weight of theresol phenolic resin, 13 to 26% by weight of the polytetrafluoroethyleneresin, and 37 to 43.5% by weight of the reinforcing base.
 2. A method ofminimizing friction between two surfaces during relative movementtherebetween in a moist environment, said method comprising the stepsof: placing a slide bearing between said surfaces, placing said surfacesin said moist environment, and moving said surfaces relative to oneanother in said moist environment, wherein the slide bearing comprises asliding contact surface-forming material comprising a reinforcing baseimpregnated with a resol phenolic resin having polytetrafluoroethyleneresin dispersed therein, the reinforcing base comprising a woven fabricformed by using a ply yarn as each of the warp and the weft,respectively, said ply yarn formed by paralleling at least two strandsof: a Z-twisted single twist yarn spun from fluorine-containing resinfiber selected from the group consisting of polytetrafluoroethylenefiber, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer fiber,tetrafluoroethylene-hexafluoropropylene copolymer fiber, andethylene-tetrafluoroethylene copolymer fiber, and a Z-twisted singletwist yarn spun from polyester fiber, and by twisting them in an S-twistin a direction opposite to the direction in which the single twist yarnswere spun; and wherein the reinforcing base is a flat-woven fabrichaving a density of 36 to 44 ends/inch for the warp (vertical yarn), and36 to 44 picks/inch for the weft (horizontal yarn), wherein the singletwist yarn spun from fluorine-containing resin fiber is a yarn of atleast 400 denier, wherein the single twist yarn spun from polyesterfiber has at least No. 30 cotton count, wherein each single twist yarnhas a twist count of 260 to 300 T/m, wherein the ply yarn has a twistcount of 255 to 295 T/m, and wherein the sliding contact surface-formingmaterial contains 37 to 43.5% by weight of the resol phenolic resin, 13to 26% by weight of the polytetrafluoroethylene resin, and 37 to 43.5%by weight of the reinforcing base.
 3. A method of minimizing frictionbetween two surfaces during relative movement therebetween in a moistenvironment, said method comprising the steps of: placing a slidebearing between said surfaces, placing said surfaces in said moistenvironment, and moving said surfaces relative to one another in saidmoist environment, wherein the slide bearing comprises a sliding contactsurface-forming material consisting of a reinforcing base impregnatedwith a resol phenolic resin having polytetrafluoroethylene resindispersed therein, said sliding contact surface-forming materialcontaining 37 to 43.5% by weight of the resol phenolic resin, 13 to 26%by weight of the polytetrafluoroethylene resin, and 37 to 43.5% byweight of the reinforcing base, the reinforcing base consisting of awoven fabric formed by using a ply yarn as each of the warp and theweft, respectively, said ply yarn formed by paralleling at least twostrands consisting of: a Z-twisted single twist yarn spun fromfluorine-containing resin fiber selected from the group consisting ofpolytetrafluoroethylene fiber, tetrafluoroethylene-perfluoroalkyl vinylether copolymer fiber, tetrafluoroethylene-hexafluoropropylene copolymerfiber, and ethylene-tetrafluoroethylene copolymer fiber, and a Z-twistedsingle twist yarn spun from polyester fiber, and by twisting them in anS-twist in a direction opposite to the direction in which the singletwist yarns were spun; and wherein the reinforcing base is a flat-wovenfabric having a density of 36 to 44 ends/inch for the warp (verticalyarn), and 36 to 44 picks/inch for the weft (horizontal yarn), whereinthe single twist yarn spun from fluorine-containing resin fiber is ayarn of at least 400 denier, wherein the Z-twisted single twist yarnspun from polyester fiber has at least No. 30 cotton count, wherein eachsingle twist yarn has a twist count of 260 to 300 T/m, and wherein theply yarn has a twist count of 255 to 295 T/m.